Loud-speaker



June 10,1930. M. c. HOPKINS 1,763,053

' I LfoUD SPEAKER original Fiied Jan. 7, '1927 2 sheetssheet 1 vente 'v -1135.12!!! v INVENTOB Lk Mara/5 C//o/o/r//f June 10, 1930. Mf c;` HoPKlNs 1,763,053

LOUD SPEAKER original Filed Jan. 7, 192,7 2 sheets-sheet 2 INVENTOR Marica/5 C /L/o/o/f/ns ATTORNEYS Patented June l0, 1930 UNITED STATESv` PATENT ori-ica MARCUS C. HOPKINS, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO TI'IJANA-` FRAM CORPORATION, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF DELA- WARE LOUD-SPEAKER Application led lJanuary 7, 1927, Serial No. 159553. Renewed` September 28, 1929.

The'present invention relates to loud speak ers of the type disclosed in my copending application, SeriaLNo. 77,033, tiled December 22, 1925, as being suitable for use with radio receiving sets or as announcers for telephone, and linewire circuits. The loud speaker' disclosed in thatl application comprises a relatively light and stili' diaphragm or tympanum preferably conical in shape and a sound board or -resonator having greater mass than that of the central diaphragm. The connection between the diaphragm and the resonator or sound board is such that the diaphragm will respond to relatively high sound frequencies and will effectively reproduce the high tones or sounds, and will also transmit relatively low frequencies through said connection to the sound board so that it will respond to the relatively low frequencies and will effectively riproduce them.` ,lt is the principal obJect of the invention there disclosetl and claimed to provide a highly efficient loud speaker capable of regenerating or reproducing sound waves directly in free air wit-hout distortion as in a horn or other amplifying device, the sound so regenerated retaining substantially the. same balance of high and low tones as the original sound from which the actuating force was derived. A

The principal object of the present invention is to provide a loud speaker of the foregoing type having a resonator of corrugated board an'd by this term l intend to include products of the type now commonly used in thev manufacture of cartons and packing" boxes, and comprising one or more plane sheets of cardlmard reinforced and stitfened by one-or more sheets of corrugatei'l cardboard.

The selection of a material suitable for use a: sound board or resonator in a loud speaker of the type above identilied is not an easy matter. The weight. of the material is of importance and must be coordinated to the weight and size of the tvmpanum or diaphragm and to the power available for actuating that tympanum or diaphragm. The

elasticity and flexibility of the sound board material are of importance, and the way in which its-fibres are grouped and are secured to one another are also of in'iportance. The wood sound board of my prior application, Serial No. 77,033 is admirably suitable for use in loud speakers of the larger size or where an adequate actuating force is readily available; whereas, for smaller sizes, that is to say, where they diameter of the rim does not exceed 2st l have found that a cork board gives excellent resultsasdescribedandclaimed in my copending application, Serial No. 121,667, tiled January 24. 19:26.

ln ar eopending application, Serial No. 87,491., tiled February 1l. 1926. I have -disclosed and claimed a loud speaker in which -the. sound hoard is formed of synthetic lumber. By the expression synthetic lumber7 I intend to include relativelyY rigid sheets or 'boards made from fibers that have been sep- 'aratedin part at least and then reassembled in a heterogeneous arrangement in a new assembly. l regard the. sounding .board of the present application as being a species of this synthetic lumber genus. but with the rigidity regulated and coordinated to the, other parts of the speaker, not by varying the pressure applied to they fibers in the press while they are being assembled` but regulated by the'thicluiess and density of the cardboard sheets which make up the presen-t board and further regulated by the corrugated character of certain of the component sheets of the present board.

I have discovered that ordinary corrugated cardboard will serve my purpose well, for it has the advantage that it is cheap in cost, easy to shape into the desired forin, is relatively resistant` to moisture. is free from warping and will withstand rough treatment during shipment and in the hands of the ultimate user. Most importantof all, it has proper acoustical properties when assembled with a sound board or a paper cone to be actuated by a radio receiving set. y

' Further objects and advantages of the present invention will become clear from the l following detailed description taken in conjunction with the accompanying drawings wherein;

Figure l is a front elevation;

Figure 2 is a vertical section of the loud speaker shown in Fig. 1;

Figure 3 is a rear elevation;

Figure 4 is a plan view; and

Figure 5 is a fragmentary section through the sound board showing its multi-ply structure.

In the drawings, the loud speaker comprises a conical diaphragm or tympanum 1 coupled to a vibratory resonator or sound board 2 by means of a flexible coupling or hinge shown in Fig. 3. The conical diaphragm 1 is preferably made of cover paper cut and folded to shape and glued on a radial seam. Near the outer edge of the cone thus formed the paper is creased and then folded up to form a forwardly Haring brim 3. 'l` his brim naturallyassumes an angle to the plane of the base of the cone equal to the angle between the radial elements of the cone and that base. The outer edge portion of the brim 3 is preferably glued to' the inner circular beveled edge of the resonator or sound board 2. The necessary beveling or tapering of the inner circular edge of the sound board as shown at 4 can readily be produced as a part of the punch press operation 'whereby the sounding board is stamped out ot a fiat panel. The inner edge portion of the brim 3 seats upon and is glued to the tapering surface thus formed. In gluing or cementing the brim to the beveled edge 4 it is important that a part of the brim be left free to form a hinge on which the cone may fioat. Thus, with the brim 9A. wide the cemented portion may have a Width of 1/4 more or less and the remainder of the brim may be left free to swing.

The resonator or sound board 2 in accordance with this invention is made of corrugated board and inthe embodiment here illustrated that board is of the kind commonly used by makers of cartons and shipping cases. It comprises a plane front lamination 5, a plane rear lamination 6 and an interposed corrugated lamination 7 glued alonof its edges to the plane boards. The outer edge of the annular sound board thus formed can be bound with a ring or band 8 of paper or Wood glued in place. The vibratory actuating force is applied to the apex of the conical diaphragm by means of a rod or wire 9 which is adapted to be maintained in fixed relation to the diaphragm by means of a set screw 10. The rod 9 may be actuated by electromagnetic mechanism. housed in a casing 11. The casing 11 may be attached to a support or spider 12 which in turn may be affixed to the resonator or sound board by bolts 13. The loud speaker may be conveniently supported by suspending it on cords attached to the spider at the eyes 14.

In constructing a loud speaker of this type I have found that excellent results are oby tained by making the cone 1531/2 in diameter and the sound board approximately Q4 in diameter. This makes the transverse width of the -annular sound board approximately 41/2, but good results may be obtained by making the sound board of less or a greater width than this. It may properly have a thickness of about l/z. The periphery of the sound board can be square or octagonal or oval. Y

In this type of speaker the central conical diaphragm eiiiciently reproduces higher tones and perhaps some of the intermediate tones, While the surrounding resonator or sound board efficiently reproduces the lower,

or bass notes. I have discovered that with a resonator made of corrugated board the reproduction of the lower or bass notes is very true and faithful. Tith this cheap and easily obtained material, as with the more expensive materials described in my copending applications, the lower notes are not only and the pieces fray at' the edges during handling in the mill. Also the completed board is inclined to warp unless special expedients are resorted to for holding it in shape.

I claim:

1. A loud speaker comprising` a conical diaphragm and a resonator of corrugated board arranged adjacent the diaphragm and adapted to be. actuated thereby.

2. A loud speaker consisting essentially ofa central diaphragm and a sound reproducing rim of corrugated board surrounding said diaphragm.

A loud speaker comprising a central conical diaphragm and a sound reproducing rim ofcorrugated hoard surrounding the diaphragm and connected thereto to permit the diaphragm. to respond to relatively high frequencies and the sound reproducing rim to respond to relatively low frequencies.

A 4. A loud speaker comprising a relatively light and sti diaphragm, an external corrugated sound board of greater mass than the diaphragm and a flexible coupling between the two adapted to permit the cliaphragi'n to respond to relatively high f'requencies and adapted to transmit the relatively low frequencies to the sound board.

5. A loud speaker comprising a central relatively light and stifl1 diaphragm, an external resonator ot' corrugated board having greater mass than the diaphragm and a fieX ible coupling between the two adapted to permit the central diaphragm to respond to relatively high frequencies and adapted to transmit the relatively7 low frequencies to said resonator.

6. A loud speaker comprising a central, conical iliaphragm, an external resonator oi greater mass than said diaphragm and a flexible*coupling between the two adapted to permit die conical diaphragm to respond to relatively high frequencies and adapted to transmit the relatively low frequencies to said resonator.

7. A loud speaker comprising a central conical diai'ihragm. an external resonator of corrugated boa-rd and a connection between said diaphragm and said board adapted to permit the central diaphragm to respond to relativelyhigh frequencies and adapted to transmit the relativelyY low frequencies to said board.

8, Aloud speaker comprising a central conical diaphragm, a corrugated board providing an annular fiange or skirt extending radially beyond the conical diaphragm and a connection between the coni al diaphragm and the board adapted to permit the coni `al diaphjagm to respond to relatively high frequencies and adapted to transmit the relatively low frequencies to said board.

9. A loud speaker comprising a central conical diaphragm having an integral forwardly Haring brim portion and a corrugated board providing a fiange portion extending radially beyond the conical diaphragm, said forwardly flaring brim portion of the conical diaphragm being attached to said board.y

10. A loud speaker comprising a conical diaphragm yrirovided with a peripheral corrugation forming a hinge portion and a corrugated board providing a flange or skirt portion extending radially beyond the conical diaphragm. said hinge portion being secured to said board. y

l1. A loud speaker comprising acorrugated board and a conical diaphragm fiexibly connected thereto so that a portion of said board extends radially beyond said conical diaphragm, the flexible connection between the conical diaphragm and the sound board being adapted to permit the conical diaphragm to respond to relatively high frequencies and being adapted to transmit the relatively low Jfrequencies to said board.

12. A loud speaker comprising a diaphragm and asound board of corrugated board connected thereto and adap-ted to be actuated thereby.

13. A loud speaker comprising a central conical diaphragm made of paper. an external corrugated board resonator, and a flexible connection between the two adapted to permit the conical diaphragm to respond to relatively high frequencies and adapted to transmit the relatively low frequencies to said board.

14. A loud speaker comprising a corrugated board resonator having a central opening, a conical diaphragm mounted in said opening. actuating means for said conical diaphragm and means f'or supporting said actuating means comprising a support attached tol said board and spanning the central opening thereof.

l5. A loud speaker comprising an annular tiat corrugated board resonator having a circular central opening. a conical diaph agm having a circular periphery. said diaphragm being mounted in said opening` and a tlexiolc coupling between said diaphragm aim 1V board adapted to permit the diaphragm io respond to relatively high frequencies and adapted to transmit the relatively low ircqucncics to said resonator.

lt. A loud speaker comprising an annular corrugated board resonator having a central opening. the edge portion of which is'pi ividcd with a tapering scat and a conical diaphragm mounted in .said opening. said diaphragm having a iorv-:ardly tlaring trusteH conical brim portion secured to said resonator on said tapering scat.

1T. loud speaker comprising'a flat annular resonator made of cm'rugatcd board. said resonator having a central opening. the edge portion ot' which is provided with a tapering seat and a fibrous conical diaphragm mounted in said opening aml having an integral jforwardly projecting brim. a part of said brim being attached to the sound board at said tapering seat.

ln testimony whereotI l atlix my signature.

MARUVH t. HOPKINS.

llO 

